Religious backgrounds of US professors circa 1969

This data comes from "a large national sample (60,000) of faculty who filled out questionnaires for the Carnegie Commission on Higher Education in 1969", as reported in "JEWISH ACADEMICS IN THE UNITED STATES: THEIR ACHIEVEMENTS, CULTURE AND POLITICS" by Seymour Martin Lipset and a co-author (pdf).

Jewish overrepresentation was even greater among faculty of elite colleges and universities, and Protestants were reduced to a bare-majority of under-30 professors at elite schools by this time.

Lipset:

The considerable presence of Jews in social science departments (and
schools of social work), in comparison to most of the humanities and
natural sciences, may be related to the disposition of secularized Western
Jews for reform-oriented politics, to be discussed later. A variety of
studies of undergraduate career choices indicate that the more left-
disposed students are more inclined than others to an academic career,
particularly in the politically relevant social sciences. 14 As the newest
group of disciplines, the social sciences have been less discriminatory,
more committed to universalistic principles than the humanities. The
latter, as the oldest and least "practical" fields, have tended to be
identified with high status, and hence were more restrictive in their
admission policies.

The underrepresentation of Jews in the humanities and history may
reflect the continuation of a distinction frequently made in Wilhelminian
and even Weimar Germany. Some who supported the appointment of
Jews to professorships in the sciences and social sciences argued that
they could not be professors of German literature or history. These
subjects were at the heart of the Volkswesen, the national essence, while
the Jews (obviously) were wesenfremd, alien to the national essence.
Suspicions about the Volkswesen suitability of Jews in English and
history have not completely vanished in the U.S. In his presidential address to the American Historical Association, in 1962, Carl Bridenbaugh
lamented that "many of the younger practitioners of our craft . . . are
products of lower middle-class or foreign origins and . . . find themselves
in a real sense outsiders to our past and feel themselves shut out. This
is certainly not their fault, but it is true." By "products of . . . foreign
origins," we would hazard the guess, Professor Bridenbaugh was not
thinking primarily of Albanians. 15